Details for: NKD2

Gene ID: 85409

Gene Type:  Protein-coding  - A gene that serves as a template for producing a messenger RNA (mRNA) molecule, which is then translated into a functional protein.

Symbol: NKD2

Ensembl ID: ENSG00000145506

Description: NKD inhibitor of WNT signaling pathway 2

Selected Context(s):  Overall

Cell Significance Landscape

Contexts:

Associated with

Significant Cells

Cell Significance Index (CSI) scores for the chosen context(s)

  • fibroblast of lung CL0002553
    CSI 4.18
    rCSI 3.89%
    PRS 98.63
  • bronchus fibroblast of lung CL2000093
    CSI 3.7
    rCSI 3.01%
    PRS 97.84
  • alveolar type 1 fibroblast cell CL4028004
    CSI 3.02
    rCSI 3.31%
    PRS 98.47
  • alveolar adventitial fibroblast CL4028006
    CSI 2.29
    rCSI 3.61%
    PRS 98.46
  • adventitial cell CL0002503
    CSI 2.23
    rCSI 5.32%
    PRS 98.65
  • basal cell of epidermis CL0002187
    CSI 1.58
    rCSI 2.8%
    PRS 79.35

Cell ID: Standard Cell Ontology term used for mapping and comparing cells across experiments. Ensures consistency in analyzing cellular functions across tissues.
Fold Change: Represents the ratio of the current Cell Significance Index to the Cell Significance Index Threshold, indicating how much the gene expression has changed compared to a baseline.
Cell Significance Index: Reflects how strongly a gene is expressed in this specific cell.

Cell ID: Standard Cell Ontology term used for mapping and comparing cells across experiments. Ensures consistency in analyzing cellular functions across tissues.
Fold Change: Represents the ratio of the current Cell Significance Index to the Cell Significance Index Threshold, indicating how much the gene expression has changed compared to a baseline.
Cell Significance Index: Reflects how strongly a gene is expressed in this cell type. Calculated using techniques like effect size estimation and bootstrapping for reliability.

Cell ID: Standard Cell Ontology term used for mapping and comparing cells across experiments. Ensures consistency in analyzing cellular functions across tissues.
Fold Change: Represents the ratio of the current Cell Significance Index to the Cell Significance Index Threshold, indicating how much the gene expression has changed compared to a baseline.
Cell Significance Index: Reflects how strongly a gene is expressed in this cell type. Calculated using techniques like effect size estimation and bootstrapping for reliability.
Network Configuration

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  • Node Color (Target Cell CSI, relative to current network):
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    • High
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  • Node Size: Proportional to Target Cell CSI magnitude
  • STRING PPI Edge
  • Shared Pathway Edge (ONTOLOGY)

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Other Information

This section provides additional information about the gene, including a description generated by an AI language model and details about associated proteins.

## Summary **[NKD2](/details-gene/85409)** (NKD inhibitor of WNT signaling pathway 2) is a protein-coding gene located on chromosome 5p15.33. The gene encodes Naked cuticle homolog 2, a protein primarily known for its role as a negative regulator of the canonical Wnt signaling pathway ([Link](https://pubmed.ncbi.nlm.nih.gov/11356022/)). Beyond its function as a Wnt antagonist, **[NKD2](/details-gene/85409)** acts as a molecular adaptor involved in protein trafficking, particularly in directing growth factors like TGF-alpha to the basolateral plasma membrane in polarized epithelial cells ([Link](https://doi.org/10.1073/pnas.0401294101)). **Overall**, expression data indicates that **[NKD2](/details-gene/85409)** is a significant marker for mesenchymal cell types, showing high specificity in various [fibroblast](/details-cell/CL0002553) populations, including those of the lung and bronchus, as well as in [adventitial cells](/details-cell/CL0002503). It also shows notable significance in [basal cells of the epidermis](/details-cell/CL0002187), suggesting a role in epithelial tissue homeostasis. ## Cellular Roles and Expression Landscape The expression profile of **[NKD2](/details-gene/85409)** points to a specialized function within structural and regenerative cell populations. **Overall**, the gene demonstrates its highest significance in several fibroblast subtypes, including [fibroblast of lung](/details-cell/CL0002553) (CSI: 4.18), [bronchus fibroblast of lung](/details-cell/CL2000093) (CSI: 3.70), [alveolar type 1 fibroblast cell](/details-cell/CL4028004) (CSI: 3.02), and [alveolar adventitial fibroblast](/details-cell/CL4028006) (CSI: 2.29). This strong and specific expression signature suggests that **[NKD2](/details-gene/85409)** is a key component of the molecular machinery governing fibroblast identity and function, particularly within the lung microenvironment. In addition to its prominence in mesenchymal lineages, **[NKD2](/details-gene/85409)** is also significantly expressed in [basal cells of the epidermis](/details-cell/CL0002187) (CSI: 1.58). This expression in a key epithelial stem cell compartment, combined with its known role in trafficking growth factors, suggests a potential role in regulating the balance between proliferation and differentiation necessary for maintaining skin barrier integrity. The collective data portrays **[NKD2](/details-gene/85409)** as a crucial regulator in both connective tissue and specific epithelial contexts. ## Pathways and Molecular Function Functionally, **[NKD2](/details-gene/85409)** operates through two primary, interconnected mechanisms: Wnt pathway inhibition and protein trafficking. Gene Ontology annotations highlight its role in the [negative regulation of the canonical Wnt signaling pathway](/details-cell/GO:0090090), a fundamental process in development and tissue homeostasis. This function is mediated by its interaction with the Wnt signaling component Dishevelled ([Link](https://pubmed.ncbi.nlm.nih.gov/11356022/)). The second major function of **[NKD2](/details-gene/85409)** is its role as a molecular adaptor ([GO:0060090](https://www.ebi.ac.uk/QuickGO/term/GO:0060090)) in intracellular transport. It is deeply involved in processes such as [exocytosis](/details-cell/GO:0006887) and the localization of proteins to the [plasma membrane](/details-cell/GO:0005886), particularly the [basolateral plasma membrane](/details-cell/GO:0016323). Seminal studies have demonstrated that myristoylated Naked2 is essential for escorting TGF-alpha-containing exocytic vesicles to the basolateral surface of polarized epithelial cells, ensuring their proper delivery and fusion ([Link](https://doi.org/10.1091/mbc.e07-02-0172)). This trafficking role is further supported by its annotated binding activities, which include [growth factor binding](/details-cell/GO:0019838) and [ubiquitin protein ligase binding](/details-cell/GO:0031625), suggesting it may also regulate protein stability ([Link](https://doi.org/10.1073/pnas.0806298105)). These dual functions position **[NKD2](/details-gene/85409)** at the intersection of major signaling and cellular transport pathways. ## Research Directions The specific expression of **[NKD2](/details-gene/85409)** in fibroblasts and basal epithelial cells, coupled with its function as a Wnt antagonist and trafficking protein, opens several avenues for future research into disease pathology and therapeutic development. ### Proposed Hypotheses: 1. **Role in Lung Fibrosis:** Given its high expression in lung fibroblasts and its function as a Wnt inhibitor, **[NKD2](/details-gene/85409)** may act as a crucial brake on pathological fibroblast activation. It is hypothesized that downregulation or functional impairment of **[NKD2](/details-gene/85409)** in lung fibroblasts contributes to the sustained Wnt signaling observed in idiopathic pulmonary fibrosis, promoting excessive extracellular matrix deposition. 2. **Regulation of Epidermal Homeostasis:** The expression of **[NKD2](/details-gene/85409)** in epidermal basal cells and its role in trafficking growth factors suggest it is a key regulator of skin integrity. It is hypothesized that **[NKD2](/details-gene/85409)**-mediated trafficking of EGFR ligands is essential for maintaining the balance between stem cell self-renewal and differentiation, and that its dysregulation could underlie hyperproliferative skin disorders or impaired wound healing. ### Experimental Approach: To test the hypothesis regarding its role in lung fibrosis (Hypothesis 1), a fibroblast-specific conditional knockout of *Nkd2* could be generated in mice (e.g., using a *Col1a2-CreERT2* driver). Following tamoxifen-induced gene deletion, pulmonary fibrosis could be induced with bleomycin. The impact of *Nkd2* loss would be assessed by comparing the extent of fibrosis (histology, hydroxyproline content), fibroblast activation markers (e.g., alpha-SMA), and Wnt pathway activity (e.g., expression of target genes like *Axin2*) between knockout and control animals using techniques like single-cell RNA sequencing and spatial transcriptomics. ### Therapeutic Potential: As an intracellular adaptor protein and a negative regulator of a pro-fibrotic pathway, **[NKD2](/details-gene/85409)** presents a challenging but potentially valuable therapeutic target. Direct targeting with small molecules is difficult. However, in diseases like pulmonary fibrosis where its function as a "brake" on Wnt signaling may be lost, therapeutic strategies would aim to **activate or restore** its function. This could involve developing small molecules that stabilize the **[NKD2](/details-gene/85409)** protein or its interaction with Dishevelled, or potentially gene-based therapies to restore its expression levels in affected fibroblasts. Inhibition of **[NKD2](/details-gene/85409)** is unlikely to be a desirable strategy for fibrotic diseases but could be explored in specific cancers driven by insufficient Wnt signaling.

Genular Protein ID: 1070030737

Symbol: NKD2_HUMAN

Name: Protein naked cuticle homolog 2

UniProtKB Accession Codes:

Q969F2 Q96EK8 Q9BSN0

Database IDs:

AGR 1 AlphaFoldDB 1 Antibodypedia 1 Bgee 1 BioGRID 1 BioGRID-ORCS 1 BioMuta 1 CCDS 2 CTD 1 ChEBI 4 DIP 1 DMDM 1 DNASU 1 DisGeNET 1 DisProt 1 EMBL 4 Ensembl 4 GO 22 Gene3D 1 GeneCards 1 GeneTree 1 GenomeRNAi 1 HGNC 1 HOGENOM 1 HPA 1 InParanoid 1 IntAct 1 InterPro 3 KEGG 1 MANE-Select 1 MIM 1 MINT 1 MassIVE 1 NCBI Taxonomy 1 OMA 1 OpenTargets 1 OrthoDB 1 PANTHER 2 PRO 1 PROSITE 1 PathwayCommons 1 PaxDb 1 PeptideAtlas 1 PharmGKB 1 Pharos 1 PhosphoSitePlus 1 PhylomeDB 1 Proteomes 1 ProteomicsDB 2 RNAct 1 RefSeq 2 SIGNOR 1 STRING 1 SUPFAM 1 SignaLink 1 TreeFam 1 UCSC 1 VEuPathDB 1 eggNOG 1 iPTMnet 1 jPOST 1 neXtProt 1

Citations:

PubMed ID: 11356022

Title: Vertebrate proteins related to Drosophila Naked Cuticle bind Dishevelled and antagonize Wnt signaling.

PubMed ID: 11356022

DOI: 10.1006/dbio.2001.0238

PubMed ID: 11604995

Title: Molecular cloning, gene structure, and expression analyses of NKD1 and NKD2.

PubMed ID: 11604995

PubMed ID: 15489334

Title: The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).

PubMed ID: 15489334

DOI: 10.1101/gr.2596504

PubMed ID: 15064403

Title: Myristoylated Naked2 escorts transforming growth factor alpha to the basolateral plasma membrane of polarized epithelial cells.

PubMed ID: 15064403

DOI: 10.1073/pnas.0401294101

PubMed ID: 17045239

Title: Structural studies of human Naked2: a biologically active intrinsically unstructured protein.

PubMed ID: 17045239

DOI: 10.1016/j.bbrc.2006.09.121

PubMed ID: 17553928

Title: Naked2 acts as a cargo recognition and targeting protein to ensure proper delivery and fusion of TGF-{alpha} containing exocytic vesicles at the lower lateral membrane of polarized MDCK cells.

PubMed ID: 17553928

DOI: 10.1091/mbc.e07-02-0172

PubMed ID: 18757723

Title: EGF receptor-independent action of TGF-alpha protects Naked2 from AO7-mediated ubiquitylation and proteasomal degradation.

PubMed ID: 18757723

DOI: 10.1073/pnas.0806298105

Sequence Information:

  • Length: 451
  • Mass: 50055
  • Checksum: F27E708F9FAD1F2A
  • Sequence:
    • MGKLQSKHAA AARKRRESPE GDSFVASAYA SGRKGAEEAE RRARDKQELP NGDPKEGPFR 
EDQCPLQVAL PAEKAEGREH PGQLLSADDG ERAANREGPR GPGGQRLNID ALQCDVSVEE 
DDRQEWTFTL YDFDNCGKVT REDMSSLMHT IYEVVDASVN HSSGSSKTLR VKLTVSPEPS 
SKRKEGPPAG QDREPTRCRM EGELAEEPRV ADRRLSAHVR RPSTDPQPCS ERGPYCVDEN 
TERRNHYLDL AGIENYTSRF GPGSPPVQAK QEPQGRASHL QARSRSQEPD THAVHHRRSQ 
VLVEHVVPAS EPAARALDTQ PRPKGPEKQF LKSPKGSGKP PGVPASSKSG KAFSYYLPAV 
LPPQAPQDGH HLPQPPPPPY GHKRYRQKGR EGHSPLKAPH AQPATVEHEV VRDLPPTPAG 
EGYAVPVIQR HEHHHHHEHH HHHHHHHFHP S